JPH046546B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an on-demand recording head for an inkjet recording apparatus, and particularly to a recording head that enables high-density mounting of nozzles.

Regarding the recording head of an inkjet recording apparatus, several systems have been devised and put into practical use.

For example, FIG. 1 is an example of a method called a drop-on-demand method. Ink is supplied from an ink tank 1 to a common ink chamber 3 of a head 2. From here, the ink flow path 4 branches into channels corresponding to pixels of the image, and leads to each nozzle 6 via a pressure chamber equipped with a piezoelectric transducer 5 driven by an individual drive circuit 9 for each channel. ing. During the recording operation, an electric signal corresponding to the image signal is applied to the piezoelectric transducer 5 attached to the pressure chamber. This pressurizes the ink,
Ink droplets are ejected from the nozzle 6 and fly.

The feature of this on-demand method is that ink is ejected only when needed in response to image signals, eliminating the need for a system to collect unnecessary ink, resulting in low ink consumption and high reliability. Moreover, the recording device itself can be made small, lightweight, and inexpensive. Another feature is that a large number of channels can be easily mounted on one recording head, so high resolution and high-speed printing performance can be obtained, and color printing is also easy.

By the way, in the system in which the nozzle 6, the ink flow path 4, and the pressure chamber 5 basically have the same direction as shown in FIG. 1, various attempts have been made to increase the density. As a result, by forming ink flow channels and pressure chambers on both sides of the recording head, it has already been possible to create a single recording head with 24 to 32 nozzles.

However, since the nozzle is tiny, there is a limit to the size of each ink flow path and pressure chamber connected to the nozzle, and it has become quite difficult to increase the density beyond the above. .

An object of the present invention is to overcome the limitations of such conventional methods in on-demand recording heads and to provide a recording head that can easily achieve higher density.

Another object of the present invention is to provide a recording head having a high density as described above, in which the drive characteristics and frequency characteristics of droplet ejection in each nozzle are substantially the same.

Still another object of the present invention is to provide a single on-demand recording head capable of high resolution and color recording.

In other words, the feature of the present invention is that the direction and arrangement of the ink flow paths and pressure chambers connected to the nozzle are substantially perpendicular to the direction of the nozzle, and are arranged radially. This eliminates the restriction that only the ink flow path and pressure chamber could be arranged.

The recording head of the ink jet recording apparatus of the present invention is an on-demand type recording head having a plurality of nozzles, an ink flow path and a pressure chamber being formed in communication with the nozzles in a direction perpendicular to the nozzles, and a piezoelectric transducer element being installed. The recording head of the inkjet recording device has a two-layer structure in which the pressure chambers and the piezoelectric transducer are arranged radially at an angle of 180° or more, and each set of the ink flow path and the pressure chamber is arranged over both the front and back surfaces. It is characterized by certain things.

That is, in FIG. 2, the length a in the longitudinal direction of the rectangular piezoelectric transducer 11 and the width b in the direction perpendicular to the longitudinal direction are such that 2b≦a≦20b. Note that the piezoelectric transducer is not limited to a rectangular shape, but may be an elliptical shape such as 12 in FIG. 2B. In this case, the length in the longitudinal direction or the maximum diameter is again considered to be a, and the width or diameter in the direction perpendicular to the length a is considered to be b.

Next, the present invention will be explained based on Examples. FIG. 3 is a diagram showing an embodiment of the present invention. Ink discharged from an ink tank (not shown) enters a common ink chamber 22 via an introduction pipe 21. The common ink chambers 22 are arranged substantially radially in a direction substantially perpendicular to the nozzle so as to surround the nozzle portion. A large number of ink channels 23 and pressure chambers 24 extend inward from the common ink chamber 22.
are arranged, and through these the nozzle 25
leading to. The nozzle 25 is installed in a direction substantially perpendicular to the ink flow path 23 and the pressure chamber 24, and in FIG. 3, it is installed toward the front side or the other side toward the page. Here, a piezoelectric transducer 26 is installed in the pressure chamber 24, but in the present invention, the shape of this piezoelectric transducer is set so that the aspect ratio is 2 or more and 20 or less, as described above. I have to. By doing this, the shape of the pressure chamber 24 can be long in the vertical direction but very small in width in the horizontal direction, compared to the case where a circular piezoelectric transducer is used, and the nozzle 25 It has become possible to install an extremely large number of ink channels 23 within a limited area around the ink flow path.
FIG. 4 shows a sectional view of the recording head of the present invention. That is, by providing a plurality of ink channels 73 and pressure chambers 74 in upper and lower layers inside both the front and back surfaces of the recording head 70, a high density of nozzles is achieved. One ink flow path 73 of the plurality of pressure chambers 74 communicates with a plurality of nozzles 75 provided on one side of the recording head 70, respectively. The other ink flow path 73 of the plurality of pressure chambers 74 communicates with a common ink chamber 72 connected to an ink tank (not shown). A piezoelectric transducer 76 is fixed to one wall surface of each pressure chamber 74 having the above-mentioned upper and lower two-layer structure, and to both the front and back surfaces of the recording head 70, respectively.

That is, by providing ink channels 73 on both the front and back sides of the recording print head, higher density is achieved.

The connection between each nozzle 25 and each ink flow path 23 is such that, for example, as in the embodiment shown in FIG. 3, ink flow paths facing each other across the nozzle row are connected to the nozzles alternately. Accordingly, it is possible to further improve the packaging density of the ink channels.

Further, the arrangement of the nozzles 25 is not limited to one row or a straight line.

For example, FIG. 5 is an example of such an arrangement method. That is, in FIG. 5A, the nozzles 51 are arranged in a matrix of n rows and m columns,
In FIG. 5B, the matrix is made oblique so that the nozzles in each row are located between the pitches of the nozzles in the other rows. By arranging the nozzles as shown in FIG. 5B, it is possible to substantially obtain high-density pixel spacing on the image recording medium while keeping the nozzle spacing wide, making head processing easy and allowing high-density recording. will be able to do it. In addition, in the nozzle arrangement method shown in Fig. 5A and B, each row is yellow, magenta,
By making it compatible with cyan, black, etc., high-density color image recording becomes possible.

FIG. 6 shows still another embodiment of the present invention. That is, the common ink chamber 22 in FIG.
By dividing the recording head into several blocks such as a, b, c, and d, a recording head for high-density color recording is created. In FIG. 6, ink introduction pipes 61 and common ink chambers 62 are provided in numbers corresponding to each color. For example, in FIG. 6, the introduction pipe 61 and the common ink chamber 62 are partitioned into four sections to correspond to the four colors of yellow, magenta, cyan, and black, and furthermore, from each common ink chamber 62, an ink flow path 63, Nozzle 6 via pressure chamber 64
5. Note that, unlike FIG. 3, in FIG. 6, each nozzle 65 is arranged in four sections corresponding to each color.

FIG. 7 shows another embodiment of the recording head according to the present invention. That is, in the recording head shown in FIG. 3, the shapes of the ink channels 23, 93 and pressure chambers 24, 94 from the common ink chambers 22, 92 to the nozzles 25, 95 are substantially the same for each channel. Moreover, the lengths are configured to be approximately equal. By configuring the recording head in this manner, it is possible to make the frequency characteristics and driving characteristics of droplets ejected from each nozzle substantially the same. Therefore, electrical control and adjustment to make the characteristics of droplets ejected from each nozzle uniform are also facilitated.

As described above, the present invention makes it possible to mount nozzles and ink ejection systems at a high density of 80 to 100 channels or more on one recording head, thereby realizing a recording head with high speed and high resolution. It became possible. In addition, the present invention enables high-speed
It has become possible to realize a color recording head with high resolution. In this way, this invention is extremely useful in practice.

[Brief explanation of drawings]

FIG. 1 is an example of a conventional multi-channel on-demand printhead. Figure 2 is an explanatory diagram of the shape of the piezoelectric transducer, Figure 5 is an explanatory diagram of the nozzle arrangement method, Figures 3, 4, 6, and 7.
The figure is an embodiment of a multi-channel on-demand printhead according to the present invention. 2, 22, 62, 72, 92 are communal ink rooms,
3, 23, 63, 73, 93 are ink flow paths, 2
4, 64, 74, 94 are pressure chambers, 6, 11, 1
2, 26, 66, 76, 96 are piezoelectric conversion elements;
5, 25, 51, 52, 65, 75, and 95 are nozzles.

Claims (1)

[Scope of Claims] 1. An on-demand inkjet recording device that has a plurality of nozzles, an ink flow path and a pressure chamber are formed in communication with the nozzles and in a direction perpendicular to the nozzles, and a piezoelectric transducer is installed. In the recording head, the pressure chambers and the piezoelectric transducer are arranged radially at an angle of 180° or more, and each set of the ink flow path and the pressure chamber has a two-layer structure arranged over both the front and back surfaces. A recording head of an inkjet recording device. 2. The inkjet according to claim 1, wherein the common ink chamber and one or more sets of ink channels, pressure chambers, and nozzles connected to the common ink chamber are divided into two or more systems. Recording head of recording device. 3. The inkjet recording device according to claim 1 or 2, wherein the shape of each ink flow path and the structure of the pressure chamber are configured so that the ejection characteristics of droplets from each nozzle are equal. record head.